This invention relates to the metering and control of fluids, and more particularly relates to the metering and control of fluids of aircraft passenger supplemental oxygen, particularly as would be used in a commercial aircraft airliner.
Emergency oxygen supply systems such as are typically installed on aircraft to supply oxygen to passengers upon loss of cabin pressure at altitudes above about 12,000 feet typically include a source of supplemental breathable oxygen connected to a face mask that is released from an overhead storage compartment when needed. The flow of breathable oxygen should be sufficient to sustain passengers until cabin pressure is reestablished or until a lower, safer altitude can be reached.
One conventional mechanical oxygen pressure regulator is powered by the output pneumatic pressure to position its valve with a programmed accurate control of oxygen supply provided by a controller that includes a processor with an algorithm stored in its memory. The processor unit responds to sensors that sense valve position, upstream pressure, downstream pressure, and external inputs received through a communication unit. An orifice inside the regulator body establishes flow between the upstream pipeline and the downstream pipeline, and a valve disc moves to occlude or partially occlude the orifice to regulate the flow between the upstream pipeline and downstream pipeline.
A conventional type of electronic pressure regulator has a microprocessor control system that provides for the valve to smoothly approach the predetermined pressure without overshoot and minimum fluctuation. The microprocessor unit controls a normally closed input solenoid valve and an exhaust solenoid valve that are responsible for the diaphragm pressure of the pressure regulator. The valves are driven with a variable pulse width and variable frequency signal based on the difference between the predetermined pressure and the present pressure, resulting in the fluctuation-free operation to the desired pressure. Another similar fluid pressure regulator includes two PID controllers. The first PID and drive controller drive the normally closed solenoid-operated valves that are the input and exhaust to the pressure regulating diaphragm. The second PID and program controller provide a feedback loop for controlling pressure to a predetermined pressure or to supplying a controlled variable output with the program being internally stored or supplied from an external source.
Another type of electronic gas regulator has a diaphragm or piston regulator of a pressure reducing valve that is controlled by an electronically driven solenoid that operates feed and bleed valves. The arrangement of the bleed and feed is a bypass loop around the main pressure regulator, and it ensures that gaseous fuels being regulated are not vented to the atmosphere, but rather are vented to the outlet of the regulator with the regulated gaseous fuel. Pulse width modulation and/or frequency modulation may be used to vary the ratio of open and closed times, and thus the output pressure, or two coils may be used instead of one, allowing independent control of the valves to compensate for inertial effects. A spring biases the piston regulator of the pressure reducing valve to a closed position in engagement with the valve seat, and a high pressure lock-off solenoid or shut-off valve with a solenoid operating coil arranged so that the lock-off solenoid is in the fully closed position when the operating coil is de-energized.
Another conventional microprocessor controlled spring-biased gas pressure regulator is controlled by a pilot valve that is automatically effected by supplying augmenting pressure to the spring side of the diaphragm via an electronically adjustable regulator valve under the control of a microprocessor that can respond to historical drop data, temperature, outdoor temperature, time of day, week, or month, or the like. The pressure regulator includes an electrically operable valve assembly having a valve-closed condition when electrically energized and a valve-opened condition in the absence of energizing voltage, which bypasses the electrically controllable pressure regulating valve when the supply of electricity is interrupted.
It would be desirable to provide a hybrid electronic and mechanical regulator that is neither a fully mechanical regulator nor a fully electronic regulator, but rather is a combination of the two approaches, offering the best of both methods. It would also be desirable to provide such a hybrid electronic and mechanical regulator in which an outlet solenoid valve is normally open, so that in the event of an electronic system failure or a power supply failure the system will automatically revert to a fully operational mechanical regulator providing outlet pressure exceeding the required level. The present invention satisfies these and other needs.